United States Health and Human Services Secretary Robert F. Kennedy Jr. has sparked widespread criticism after falsely claiming a link between autism and circumcision. Despite his assertions, there is no credible scientific evidence supporting this claim, according to multiple peer-reviewed studies and public health experts.

On October 9, 2025, Kennedy stated that “two studies show children circumcised early have double the rate of autism,” adding that the correlation was “highly likely because they’re given Tylenol.” Both experts and official data have since debunked this claim, describing it as misleading, unsupported, and scientifically unsound.

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Understanding the Claim

Kennedy’s comments stem from his long-standing skepticism toward mainstream medicine and vaccines. His recent statement linked circumcision, a routine surgical procedure, with the use of acetaminophen (Tylenol) in infants — suggesting this combination causes autism.

However, the research Kennedy cited (from 2013 and 2015) does not establish causation. Neither study measured acetaminophen use, and both explicitly cautioned against interpreting their results as proof of a link.

“Neither study demonstrates that circumcision causes autism,” experts confirmed. “Correlation is not causation.”

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Examining the Studies

1. The 2013 Study: A “Hypothesis-Generating” Paper

Conducted by epidemiologists at UMass-Lowell, this exploratory study sought to determine whether acetaminophen exposure could be associated with autism risk. Circumcision was analyzed as a proxy variable, not the study’s focus.

Key flaws include:

• A tiny sample size (data from just nine countries).
• Use of estimated circumcision rates based on religious demographics.
• No confirmation that acetaminophen was actually administered.

The authors themselves stated that their findings were preliminary and required “further research to confirm or disprove this association.”

“The study was never designed to prove causation,” said Helen Tager-Flusberg, a professor emerita at Boston University and founder of the Coalition of Autism Scientists.

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2. The 2015 Danish Study: Small Samples, Big Misinterpretations

The 2015 research conducted in Denmark examined 342,877 boys born between 1994 and 2003. It found that circumcised boys were 46–62% more likely to receive an autism diagnosis before age 10. However, the findings were statistically unstable:

• Fewer than 1% (3,347) were circumcised.
• About 1.5% (5,033) had autism.
• Only 57 boys had both conditions.

The small overlap between these groups made it impossible to draw reliable conclusions. Researchers warned against overinterpreting the correlation, emphasizing the potential for confounding factors like cultural background and socioeconomic differences.

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What Experts Say

Health experts overwhelmingly reject the notion that circumcision — or acetaminophen — increases autism risk.

• Acetaminophen has been used safely for decades under pediatric supervision.
• Circumcision is typically performed with local anesthesia, and acetaminophen is sometimes given for mild post-procedure pain, but not universally.
• No major medical body, including the World Health Organization (WHO) or U.S. Centers for Disease Control and Prevention (CDC), recognizes any link between these practices and autism.

“Neither of these studies considers the range of cultural, demographic, or biological factors that influence autism diagnoses,” said Tager-Flusberg.

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Kennedy’s Use of an Unpublished 2025 Preprint

In an October 10 post on X (formerly Twitter), Kennedy referenced a 2025 preprint by WPLab, a private North Carolina research company that promotes the Tylenol-autism theory.

The preprint has not been peer-reviewed, meaning it has not undergone scientific validation. It largely recycles old arguments, claiming that “acetaminophen exposure triggers most autism spectrum disorder cases.” The paper does not present new data and misrepresents findings from the 2015 Danish study.

WPLab CEO William Parker, a retired Duke University professor and ally of Kennedy, has been accused of spreading pseudoscience. His company’s work has been discredited by independent scientists for lacking transparency and methodological rigor.

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Scientific Consensus

The scientific community remains united in its assessment:

• Autism has complex genetic and environmental causes, but no credible link to circumcision or Tylenol use.
• Multiple large-scale studies and meta-analyses have found no evidence that acetaminophen use during infancy or pregnancy increases autism risk.
• The American Academy of Pediatrics (AAP) continues to affirm that both circumcision and acetaminophen are safe when used properly.

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The Bottom Line

Robert F. Kennedy Jr.’s claim that circumcision causes autism is false.
The studies he cites are misinterpreted, statistically weak, and non-causal. The supposed “new evidence” he references is unpublished and unverified.

Experts warn that spreading misinformation about medical practices like circumcision or pain relief medication can lead to public confusion, unnecessary fear, and decreased trust in healthcare systems.

“Scientific integrity requires evidence, not anecdotes,” said a statement from the Coalition of Autism Scientists. “The data simply do not support Kennedy’s claims.”